1. Field of the Invention
The present invention relates to a workover and drilling rig for use in servicing and stimulating existing wells and drilling new wells for the production of fluids from subterranean formations. The present invention is particularly suited for use in oil and gas production.
2. Description of the Related Art
Truck or trailer-mounted conventional drilling and workover rigs are typically of either of two basic types. The first type, which is used for conventionally threaded tubulars, consists of the combination of a mobile supporting platform (e.g., a trailer or a truck bed) and an elevatable rig mast. The second type, which is used for coiled tubing, consists of a mobile supporting platform, a coiled tubing reel, a levelwind mechanism, and a conventional opposed track tubing injector. In both cases, pumps and other peripheral equipment are often included. The advantages and disadvantages of these types of workover rigs are well known. While these conventional rigs are readily transportable, easy to rig up and down, and economical, they are limited to use with either one or the other type of tubular.
A mobile combination coiled tubing and threaded tubing rig has been developed by Coiled Tubing Solutions, of Eastland, Tex. 76448. This combination rig uses a wheel type injector mounted in the mast with its axis of rotation above midheight of the mast. Additionally, a coiled tubing reel with an independent levelwind mechanism is mounted on the mobile supporting platform of the rig. This combination rig is very top heavy and wind sensitive. Furthermore, when the mast is stowed, the weight distribution of the rig is overly concentrated on the forward end of the truck or trailer on which the rig is mounted. Additionally, this type unit is limited in coiled tubing size because of highway vehicle height limits and their attendant limitations on reel and injector wheel size. This limitation arises because of the projection of the injector wheel above the bed of the trailer or truck used for the mobile platform. In addition, the coiled tubing must be inserted into the wheel injector after the mast is elevated and removed before the mast is lowered.
A need exists for an improved combination workover and drilling rig that can raise and lower the coiled tubing injector independently from the raising and lowering of the conventional rig mast.
Furthermore, there is a need for a combination workover and drilling rig that permits the coiled tubing to be engaged by the tubing injector at all times.